Fuel Cell Stack Impedance Measurement Relay Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Accurately measuring the impedance of a fuel cell stack during vehicle operation is challenging due to the difficulty in maintaining a steady state and the influence of peripheral components on the measurement.
Innovation Solution
A method involving the use of relays to isolate the fuel cell stack from peripheral devices, controlling air supply to maintain a steady output current, and monitoring the battery's state of charge to ensure accurate impedance measurement across various frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impedance measurement is performed during vehicle driving with the fuel cell stack connected to peripheral components, then the measurement can be conducted in actual operating conditions, but the measurement accuracy is reduced due to the influence of peripheral component impedance
Solution Approach 1:
The patent extracts the fuel cell stack from the complex vehicle power system by using relays to isolate it from peripheral components (battery, motor, etc.) during impedance measurement. This creates a simplified measurement circuit that includes only the fuel cell stack, impedance meter, and load, eliminating the influence of peripheral component impedance on the measurement accuracy.
Solution Approach 2:
The patent introduces relays as intermediary components to control the connection and disconnection between the fuel cell stack and peripheral components. These relays act as mediators that enable the system to switch between normal operating mode (with peripheral components) and measurement mode (isolated fuel cell stack), thereby resolving the contradiction between actual operating conditions and measurement accuracy.
2Stability of the object's composition
If the fuel cell stack operates in a steady state at a predetermined operating point, then impedance measurement can be performed, but it is difficult to maintain this state during vehicle driving
Solution Approach 1:
The patent applies preliminary action by pre-charging the battery to a reference state of charge value before isolating the fuel cell stack for impedance measurement. This preliminary charging ensures that when the stack is isolated and connected to the load, it can quickly reach and maintain the predetermined operating point without being affected by variable vehicle loading conditions, thereby reducing the time needed to establish a stable measurement state.
Solution Approach 2:
The patent uses relays to dynamically reconfigure the system topology, switching from a complex variable-load vehicle operating mode to a controlled constant-load measurement mode. This dynamic reconfiguration allows the fuel cell stack to transition to and maintain a steady state more quickly by eliminating the disturbances from peripheral components.
3Measurement precision
If relays are used to isolate the fuel cell stack from peripheral components for accurate measurement, then measurement accuracy is improved, but the system complexity and control requirements increase
Solution Approach 1:
The patent implements self-service by integrating the relay control logic directly into the fuel cell control system. The control unit automatically determines when impedance measurement is needed, activates the appropriate relays to isolate the stack, manages the battery pre-charging process, and controls the load connection without requiring external intervention. This automation simplifies operation despite the added hardware complexity.
Data Source
AI summary
A method of measuring impedance of a fuel cell stack in a vehicle during driving of the vehicle includes: determining whether an impedance measurement of the fuel cell stack is requested during driving of the vehicle driven by power of the fuel cell stack; turning off a first relay connected between the fuel cell stack and a battery charged by the fuel cell stack when the impedance measurement of the fuel cell stack is requested; connecting a stack load to the fuel cell stack via a second relay and supplying air to the fuel cell stack; and measuring the impedance of the fuel cell stack.